Autoradiography of Photomembrane in HEMIGRAPSUS NUDUS

Protein synthesis was studied in the visual cells of Hemigrapsus nudus by light microscope autoradiography. Two hours before sunset, crabs were injected with a single dose of tritiated leucine and sacrificed at time intervals coincident with dynamic retinal changes observed in electron microscope (EM) studies of related Arthropods (Blest, 1978 and Stowe, 1980). Two separate experiments were performed to examine time periods in the renewal process. Some periods in each experiment were overlapped to develop more accurate decay curves. Experiment I followed time regimes of 0.5, 1.5, 2.5, 3.0, 3.0, 5.0, and 6.0 hours after sunset. Autoradiographs of retinula cells were examined for temporal variations in grain concentration and in spatial distribution patterns. The concentration of leucine in the retinula cells peaked at 1.5 hours, declined until the third hour, and leveled off through hour six. Region II peripheral to the rhabdome showed the highest concentration for all sample times. In Experiment II, greater resolution of peak times for grain concentration was obtained using sacrifice regimes of 0.0, 0.5, 1.0, 1.5, and 2.5 hours after sunset. Also evaluated were temporal variations in rhabdomeral-cystoplasmic distribution. Other retinula cells were sampled at 0.5 and 1.0 hours after injection to determine the path of newly-synthesized protein before induction of the dark phase. Finally, similar evaluations of grain count and distribution were performed on autoradiographs of visual cells at sunrise (sample times: 0.0, 1.0, 2.0 hours after sunrise) and after long-term exposure to tritiated leucine (sample times: 1, 2, and 7 days after injection, maintaining normal 12:12 Light:Dark conditions). Results from Experiment II showed a peak time for grain concentration to be closer to 1.0 hour after sunset rather than the 1.5 hours of Experiment I. Spatially, labeled protein was more concentrated within the cytoplasm until 0.5 hour after sunset, when the higher proportion of grains shifted to the rnicrovilli, the area specialized for light absorption. Long-term samples continued to show the same spatial differentiation while declining in overall count

GABA as a Putative Neurotransmitter in the Optic Lobes of the Crab HEMIGRAPSUS NUDUS

Gamma-aminobutyric acid ( GABA ) is a widely occurring inhibitory neurotransmitter in vertebrate and invertebrate neural tissue. To explore the role of GABA as a putative neurotransmitter in the optic lobes of the crab Hemigrapsus nudus, light microscope autoradiography ( LM ARG ), light microscope immunocytochemistry ( LM ICC ), and neurochemical techniques were employed. ARG labeling of 3H-GABA was observed over specific neuronal cell bodies and axon fibers in the two outer optic neuropils, the lamina ganglionaris and the medulla externa. Biochemical analysis of 3H-GABA uptake revealed little surface receptor binding as picrotoxin and bicuculline did not appear to effect uptake. Similar biochemical experiments showed little glial . involvement. 2,4-diaminobutyrate ( L-DABA ), shown in other studies to preferentially inhibit uptake by neurons but not glia, matched the degree of inhibition of uptake seen by unlabeled GABA, which affects uptake by neurons and glia equally. p-Alanine, which has the reverse effect of L-DABA, reduced uptake only slightly more than seen in untreated eyes. Hence, ARG labeling was primarily intracellular and confined to neurons. LM ICC staining of GABA was found in specific neurons in the same regions of the neuropils which tested positive by ARG. In addition to verifying the presence of endogenous GABA, ICC findings support the assumption that uptake of exogenous GABA occurs in cells that contain and presumably use that transmitter. Neurochemical analysis of uptake describe a high-affinity, sodiumdependent, metabolically active process, findings similar to uptake mechanisms described for GABA in vertebrate central nervous system and retinal tissue. Release of label from preloaded eyes was effected in a dose-dependent manner using high concentrations of potassium. Neither uptake nor release appeared to involve the cytoskeletal elements actin or tubulin as cytochalasin B and colchicine did not effect either process. Results described above establish GABA as a putative neurotransmitter in the optic lobes of the eye of Hemigrapsus nudus. Demonstration of the presence of endogenous GABA in specific neurons, uptake of 3H-GABA into specific neurons by a high-affinity, sodium-dependent, metabolically active process, and demonstration of release of 3H-GABA satisfy half of the criteria for establishing a substance as a neurotransmitter

Dynamic planning and control for large-scale infrastructure projects : route 3N as a case study

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2002.Includes bibliographical references (leaves 131-137).by Margaret Fulenwider.S.M

Social Housing Leads to Increased Ethanol Intake in Male Mice Housed in Environmentally Enriched Cages

An individual's social environment affects alcohol intake. However, the complex interactions between social context and alcohol intake remain understudied in preclinical models. In the present study, we sought to characterize the effects of social housing on voluntary ethanol intake in male C567BL/6J mice using a continuous access two-bottle choice model. This was accomplished using HM2 cages, which allow for the continuous monitoring of individuals' fluid intake through radiofrequency tracking while they remain undisturbed in a group setting. These cages are moderately environmentally enriched compared to standard shoebox cages. By analyzing the levels of voluntary ethanol intake between socially- and individually-housed mice in HM2 cages, we were able to parse apart the effects of environmental enrichment vs. social enrichment. We found that while intake levels were overall lower than those observed when animals are singly housed in standard shoebox cages, socially-housed males consumed significantly more ethanol compared to individually-housed mice, suggesting that while environmental enrichment attenuates ethanol intake, social enrichment may, in fact, potentiate it. This effect was not specific for alcohol, however, in that ethanol preference did not differ as a product of social context. We also found that the total number of non-consummatory channel entries were consistently higher in individually-housed mice. Additionally, a single corticotropin releasing factor receptor 1 antagonist treatment significantly decreased both water and ethanol intake in socially- and individually-housed mice up to 3 h post-treatment, though the effect on water intake was longer lasting. This treatment also significantly decreased the number of non-consummatory channel entries in individually-housed mice, but not in socially-housed mice, suggesting that increased channel visits may be a stress-related behavior. Lastly, we examined blood ethanol concentrations and FosB immunoreactivity to characterize the physiological responses to ethanol intake in socially- and individually-housed mice. The number of FosB-positive cells in the centrally-projecting Edinger-Westphal nucleus and nucleus accumbens shell positively correlated with average baseline ethanol intake in individually-housed mice, but not in socially-housed mice. Overall, we found that social, but not environmental, enrichment can increase ethanol intake in male C57BL/6J mice. Future studies need to test this phenomenon in female mice and assess the generalizability of this finding

13C-phenylalanine breath test detects altered phenylalanine kinetics in schizophrenia patients

Phenylalanine is an essential amino acid required for the synthesis of catecholamines including dopamine. Altered levels of phenylalanine and its metabolites in blood and cerebrospinal fluid have been reported in schizophrenia patients. This study attempted to examine for the first time whether phenylalanine kinetics is altered in schizophrenia using L-[1-13C]phenylalanine breath test (13C-PBT). The subjects were 20 chronically medicated schizophrenia patients (DSM-IV) and the same number of age- and sex-matched controls. 13C-phenylalanine (99 atom% 13C; 100 mg) was administered orally and the breath 13CO2 /12CO2 ratio was monitored for 120 min. The possible effect of antipsychotic medication (risperidone (RPD) or haloperidol (HPD) treatment for 21 days) on 13C-PBT was examined in rats. Body weight (BW), age and diagnostic status were significant predictors of the area under the curve of the time course of Δ13CO2 (‰) and the cumulative recovery rate (CRR) at 120 min. A repeated measures analysis of covariance controlled for age and BW revealed that the patterns of CRR change over time differed between the patients and controls and that Δ13CO2 was lower in the patients than in the controls at all sampling time points during the 120 min test, with an overall significant difference between the two groups. Chronic administration of RPD or HPD had no significant effect on 13C-PBT indices in rats. Our results suggest that 13C-PBT is a novel laboratory test that can detect altered phenylalanine kinetics in chronic schizophrenia patients. Animal experiments suggest that the observed changes are unlikely to be attributable to antipsychotic medication

Modular Laser Combat System for Remotely Operated Vehicles: Bridging the Gap Between Computer Simulation and Live Fire

In the emerging industry of small unmanned vehicles, pioneered by small businesses and research institutions, a suitable combat system test platform is needed. Computer simulations are useful, but do not provide the definitive proof of effective operation necessary for deployment of a combat system. What is needed is an affordable simulated weapons system that enables live flight testing without the used of live weaponry. A framework is developed here for the construction of a simulated weapon using Free Space Optical (FSO) infrared communication. It is developed in such a way to ensure compatibility with a variety of platforms including ground and aerial vehicles, so that identical but configurable modules can be used on any vehicle that is to take place in a live combat simulation. A proof-of-concept implementation of this modular laser combat system framework is also presented and tested. The implemented system shows the value of such a simulated weapons system and future areas of improvement are also explored